Control apparatus



Dec. 5, 1939. R. H. HERRICK 3 CONTROL APPARATUS Filed March 19, 1958ATTORNE 'Y$.

a a j 1" I Vo/faqe a. q 1 l v ohn- P P J, B i F 2 Mm I ROSWELL H.HERRICK m Patented Dec. 5, 1939 UNITED STATES CONTROL APPARATUS RoswellHarry Herrick, Oak Park, IlL, assignor to Associated ElectricLaboratories, Inc., Chicago, 11]., a corporation of Delaware ApplicationMarch 19,

12 Claims.

The present invention relates to control apparatus and more particularlyto improvements in impulse responsive relay networks wherein electronicdevices are utilized to control electro- 'magnetic relays comprisingimpulse repeating apparatus. I

In an arrangement of the character mentioned, the input or controlvoltage is usually impressed on the input electrodes of an electrondischarge device having included in its output circuit a control relayor other electromagnetic control device which is traversed by theanodecurrent of the controlling electron discharge device: In time, the anodecurrent flowing through the relay winding causes residual magnetism tobe developed in the core of the relay. As a consequence, the relay isprevented from properly responding to variations in the voltageimpressed on the input electrodes of the controlling electron dischargedevice. This problem is particularly troublesome in networks wherein thecontrol relay and the electron discharge device arearranged to respondto the impulses of an impulse train, such, for example, as impulsetrains of the character utilized in controlling automatic switchesconventionally used in automatic telephone systems. More particularly,in an impulse responsive network of this character, it is highlydesirable to utilize the steep linear portion of the grid voltage-anodecurrent characteristic of the electron discharge device asthe operatingrange within which the grid voltage is varied in response to receivedimpulses. By utilizing this portion of the characteristic curve, it ispossible to obtain the maximum change in the anode current traversingthe control relay winding for a given change in the input voltageimpressed on the input electrode of the electron discharge device. Whenthis portion of the-characteristic curve is used, however, the electrondischarge device usually is not, even during. periods of non-use,

biased beyondcutoiI and; hence, a steady direct anode currentcontinuously traverses the winding- 1938, Serial No. 196,919

positive response of the control device to changes in the input voltageimpressed on the input electrodes of the electron discharge device is attained.

It is a further object of the invention to provide an improved impulseresponsive network of the form described wherein the character of theoutput or repeated impulses is, within limits, substantially independentof the character oi the received impulses. 10

In the illustrated embodiment of the invention, there is shown a pulsingrelay including a winding and a control armature, a condenser, a sourceof potential for charging the condenser, and a. second relay foralternately connecting the condenser to be charged from the source andto discharge through the winding of the pulsing relay, thereby to causealternate operation and restoration of the control armature. For thepurpose of controlling the second relay, there is provided an electrondischarge device including an input electrode and output electrodes,with suitable apparatus for impressing pulses of input voltage on theinput electrode. The second relay, mentioned above, is connected. andarranged to be energized in accordance with the current flowing in theoutput circuit of the electron discharge device. In order to render thissecond relay positive in operation or to obviate the difliculty asmentioned above, there is also provided circuit apparatus for passing asecond current through the winding of the second relay in opposition tothe. anode current of the electron discharge device, and of a magnitudesubstantially different in one sense than the magnitude of the anodecurrent when impulses of input voltage are impressed on the inputelectrode of the electron discharge device. Further to accomplishthisend, additional apparatus is provided for changing the magnitude ofthe anode current to a value different in the said one sense than thevalue of the second or opposing current during the intervals when noinput voltage is impressed on the input electrode of the electrondischarge device. By this arrangement, the direction of current flowthrough the winding of the second relay is reversed at the beginning andend of each pulse of input voltage impressed on the input electrode ofthe electron discharge device and theeflects of residual magnetism aresubstantially obviated. In order to render the repeated or outputimpulses of the impulsing relay substantially independent'of the pulsesof input voltage applied to the input electrode of the electrondischarge device, an additional impedance element is provided in shuntwith the winding of the pulsing relay; and the impedance of the windingof the impulsing relay, the capacitance of the condenser for energizingthis winding,and the impedance of the additional impedance element areso proportioned relative to each other that theratio of the restoredintervals to the ,operated intervals of the pulsing relay is, withinlimits, independent of the ratio of the corresponding periods for therelay having its winding included in the output circuit of the electrondischarge device.

The novel features believed to be characteristic of the invention areset forth with particularity in the appended claims. The invention,

' both as to its organization and method of opera- H and to repeat theseimpulses over a circuit including the terminals l2 connected to armaturesprings controlled by an armature l3 of a pulsing relay H. The networkcomprises an electron discharge device |5in the form of a vacuum tubehaving an input electrode or control grid Hi and a pair of outputelectrodes comprising a cathode l1 and an anode l8. The transformer IIis provided with a secondary winding |9-which is coupled between theinput electrode l6 and the cathode I! by a capacitance element 20.Coupled to the output electrodes of the device I5 is an output circuitwhich comprises the winding 2| of a control device or relay 22 and theportion 23 of a voltage dividing resistor 24. The resistor portion 24and the winding 2| are by-passed for alternating currents by acapacitance element 25. In order that the grid voltage of the dischargedevice l5 may be varied withinthe optimum or steep linear portion of itsgrid voltage-anode current characteristic in response to pulses of inputvoltage during operation of the network, the source of bias voltagecomprising the drop across the portion 26 of the resistor 24 is arrangedto vbe. impressed by way of circuit connections including the secondarywinding IQ of the transformer II on the input electrode ii. In order toobviate the difficulty mentioned above or to insure positive response ofthe relay 22 to variations in input voltage, a priming circuit is pro-'vided for passing a current through the winding 2| of this relay inopposition to the anode current normally flowing in the output circuitof the electron discharge device ID. This priming circuit includes'aportion 21 of the resistor 24 and a second resistor. 28 of relativelyhigh resistance. A source of direct voltage, not shown, is connectedbetween the terminals +13 and B of the voltage dividing resistor 24.

The relay 22 is provided with an armature spring 29 which is arranged tobe-operatedbetween two contacts '3|l and 2| to control the energizationand deenergization of the pulsing relay l4. More particularly, thearmature 29 is connected to one electrode one. condenser '32 which sideof the resistor portion 24.

is arranged to be charged over two conductors 33-and 34 from a source ofvoltage, not shown, but having its terminalsconnected to the terminals35 and 36. A circuit comprising the conductor 34 and a third conductor31 is provided Fig. 1 may best be described by reference to the,

graph illustrated in Fig. 2. In brief, when the network is conditionedfor operation and no alternating current impulses are impressed be tweenthe input terminals Ill of the transformer ll, two components of currentare flowing through the winding 2| 'of the relay 22. The first of thesecomponents of current is the anode current which flows from the +Bterminal of the voltage supply source by way of the anode IS, theelectron stream between this anode and the .cathode I1, the winding 2|to the negative The magnitude of this first component of current isdetermined by the bias impressed on the input electrode I6 of theelectron discharge device l5, and, preferably, this bias is chosen bf avalue 6b which corresponds to the knee of ,the grid voltage-anodecurrent curveA, whereby the steep linear portion of the curve lyingbetween a and b may be utilized as the range within which the gridvoltage is varied when an impulse of input current is impressed on theinput terminals "I. With a bias voltage of en, the anode current or thefirst component of current flowing through the winding 2|.

"position to- .the anode current, since it flows from the positive sideof the resistor portion 2'! by way of the winding 2| and the resistor 28to the negative side of the resistor portion 21. Hence, the secondcomponent pf current may be designated as being of negative polarity.This I second component of current, the magnitude of which is indicatedin Fig. 2 is at is is substantially diflerent in one sense; that is, itis substantially greater than the anode current in when no input voltageis impressed between the input terminals I of the transformer II. Thenet current flowing through the winding 2| is the diiference between thetwo currents i and in and is indicated in Fig. 2 as being of a magnitudein, which is of a negative polarity. The magnitude of the current in ismaintained at a value less than the value of current required foroperation of the relay 22 and, hence, this 'relay remains restored whenno input voltage is impressed between the terminals l0. By

\ suitably proportioning the resistance value of pointed out that theresistance of the priming circuit and, more particularly, the resistor28, is made high relative to the resistance of the winding 2 I, so thatno substantial portion of the direct component of the anode currentflowing in the output circuit of the device I5 is by-passed around thewinding 2|.

With the relay '22 restored, the condenser 32 is connected by way of thecircuit including the two conductors 33 and 34, the contact and thearmature 29 across the source of voltage connected between the terminalsand 36. Thus, the condenser 32 is charged to the voltage existingbetween the terminals 35 and 36. When a received pulse of alternatingvoltage, as indicated at B, is applied to the terminals Hi, this voltageis impressed between the input electrode I6 and the cathode l'l throughthe transformer H and the coupling condenser 20. On one-half of eachcycle of this voltage, the negative potential on the electrode I6 isreduced to a value 61) so that the anode current is increased to atheoretical maximum value im. The average or effective value of thecurrent flowing in the anode circuit of the device |5 during repeatedpositive half cycles of the input voltage is something less than the theopposing component current 1' flowingthrough the winding 2| as aconsequence of the provision of the priming circuit. The differencebetween the two components of current is indicated at 1'0. This currentis of a positive polarity and is above the value required to causeoperation of the relay 22. As a consequence, this relay operates to movethe armature 29 from engagement with thecontact 30 and into engagementwith the contact 3| so that the charged condenser 32 discharges throughthe winding of the relay H and the condenser 38 in parallel. Thiscurrent is sufficient to cause the operation of the relay I4 so that thearmature 3 is moved into engagement with its associated contact torepeat the pulse over the circuit connected to the terminals l2. thatthe alternating input voltage 3 is no longer applied to the inputelectrode IS, the anode current is reduced from the average value in tothe steady state value in. When this occurs, the priming current ipagain predominates and the net current flowing through the winding 2| isreduced to the negative value in. Hence, the relay 22 is caused torestore to reconnect the condenser 32 to again be charged from thevoltage cource connected to the terminals 35 and 35.

During each succeeding pulse of input voltage impressed on the theelectrode IS, the above-described sequence of operations is repeated;

From the foregoing description it will be ap parent that, during aseries of received impulses, the direction of current flow through thewinding 2| of the relay 22 is reversed at the beginning and the end ofeach pulse of input voltage. Thus, the effect of any residual magnetismwhich may be developed in the core of the relay 22 is substantiallyobviated. It will also be noted that, by normally biasing the dischargedevice |5 to the knee of its grid voltage-anode current characteristiccurve, the steep and relatively linear portion of the curve lyingbetween the points a and b is the operating range of the curve throughwhich Obviously, when the pulse is ended, so

the grid voltage is normally varied when the input voltage pulses areimpressed on the electrode I6. By biasing the tube to this point, themaximum change in the anode voltage is secured for a given change in thevoltage applied to the electrode l6. tion of the specification, theparticular arrangement of the circuit for energizing the pulsing relayI4 is such that the ratio of the closed contact period to the opencontact period of this relay during each impulse may, within limits, berendered independent of the ratio of the corresponding periods for therelay 22. More particularly, when the relay 22 is operated to connectthe condenser 32 to discharge through the winding of the relay M, thetime interval during which the last-mentioned relay will be sufiicientlyenergized to stay operated depends upon the time constant of the circuitincluding this winding, the condenser 38 and the charge condenser 32. Bysuitably proportioning the capacitance of the condenser 32, thecapacitance of the condenser 38, and the impedance of the winding of therelay l4 relative to each other, the time constant of the circuit may berendered such that the relay M will restore before the restoration ofthe relay 22 or, alternatively, willremain operated during the entireinterval when the relay 22 is operated.

Again, by suitably proportioning the capacitance of the condenser 38with respect to the impedance of the winding of the relay M, thedemagnetization of this relay at the end of each period of 'energizationmay be delayed sufliciently so that the relay M will remain operatedafter the restoration of the relay 22. Thus, by suitably varying thecapacitance values of the two condensers 32 and 38, the portion of eachimpulsing period during which the relay I4 is operated may be variedwithin wide limits. By this arrangement, the ratio of the open circuitto the closed circuit periods of the circuit connected to the terminals|2 may be adjusted to suit the requirements of any particularapplication.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be understood thatvarious modifications may be made therein, and it is intended to coverin the appended claims all such modifications as fall within the truespirit and scope of the invention.

What is claimed is:

1. An impulse responsive network comprising, in combination, a' firstrelay including a winding and a control armature, a condenser, a sourceof potential for charging said condenser, a second relay for alternatelyconnecting said condenser to be charged from said source and todischarge through the winding of said first relay, thereby to causealternate operation and restoration of said control armature, an elctrondischarge device including an input electrode and output electrodes,means for impressing pulses of input voltage on said input electrode, anout- 1 put circuit coupled .to said output electrodes, said second relayincluding a winding connected and arranged to be energized inaccordancewith the current flowing in said output circuit, means for passing asecond-current through the winding of I said second relay in oppositionto said first-mentioned current and of a magnitude substantiallydifferent in one sense than the magnitude of said As indicated in theintroductory por output electrodes, a control device having a windingconnected and arranged to be traversed by a v current which variessubstantially in accordance 'with the current flowing in said outputcircuit,

source of biasing potential, circuit connections for impressing thevoltage of said source on said input electrode, and means including saidsource and said circuit connections for changing the magnitude of saidfirst-mentioned current to a value different in said one sense than thevalue of said second current when the input voltage impressed on saidinput electrode is reduced to a predetermined value, whereby thedirection of current flow through said winding is reversed when saidinput voltage is decreased from said substantial value to saidpredetermined value and when said input voltage is increased from saidpredetermined value to said substantial value '7. Electrical controlapparatus comprising, in combination, an electron discharge deviceincluding input and output electrodes, an input circuit coupled to saidinput electrodes and adapted to have an input voltage impressed thereon,an output circuit coupled to said output electrodes, a control devicehaving a winding connected and arranged to be traversed by a currentwhich varies substantially in accordance with the current flowing insaid output circuit, means for passing a second current through saidwinding in opposition to said first-mentioned current and of a magnitudesubstantially less than the magnitude of said first-mentioned currentwhen any substantial input voltage is impressed on said input circuit,and means for decreasing said firstmentioned current to a value lessthan that of said second current when the input voltage impressed onsaid input circuit is reduced to a predetermined value, whereby thedirection of current flow through said winding is reversed when arrangedto be traversed by a current which va-.

ries substantially in accordance with the current flowing in said outputcircuit, means for passing a second current through said winding inopposition'to said first-mentioned current and of a magnitudesubstantially less than the magnitude of said first-mentioned currentwhen any substantial input voltage is impressed on said input circuit, asource of biasing potential, circuit connections for impressing thevoltage of said source on said input electrode, and means including saidsource and said circuit connections for decreasing said first-mentionedcurrent to a value less than that of said second current when the inputvoltage impressed on said input circuit is reduced to a predeterminedvalue, whereby the direction of current flow through said winding isreversed when said input voltage is reduced from said substantial valueto said predetermined value and when said input voltage is increasedfrom said predetermined value to said substantial value.

9. Electrical control apparatus comprising, in combination, an electrondischarge device including an input electrode and output electrodes,means for impressing an input voltage on said input electrode, an outputcircuit coupled to said output electrodes, a control device having awinding connected in said output circuit to be traversed by the currentflowing in said output circuit, a priming circuit including a voltagesource for passing a second current through said winding, said primingcircuit being so connected and arranged that said second current is inopposition.

to said first-mentioned current and is of a magnitude substantiallydifi'erent in one sense than the magnitude of said first-mentionedcurrent when any substantial input voltage is impressed on said inputelectrode, and means for changing the magnitude of said first-mentionedcurrent to a value diiferent in said one sense. than the value of saidsecond current when the input voltage impressed on said input electrodeis reduced to a predetermined value, whereby the direction of, currentflow through said winding is reversed when said input voltage isdecreased from said substantial value to said predetermined value andwhen said input voltage is increased from said predetermined value tosaid substantial value.

10. Electrical control apparatus comprising, in combination, an electrondischarge device including an input electrode and output electrodes,means for impressing an input voltage on said input electrode, an outputcircuit coupled to said output electrodes, a control device having awinding connected in said output circuit to be traversed by the currentflowing in said output circuit, a priming circuit including a voltagesource for passing a second current through said winding, said primingcircuit being so connected and arranged that said second current'is inopposition to said first-mentioned current and is of a magnitudesubstantially different in one sense than the magnitude of saidfirst-mentioned current when any substantial input voltage is impressedon said input electrode, a source of biasing potential, circuitconnections for impressing the voltage of said source on said inputelectrode, and means including said source and said circuit connectionsfor changing the magnitude of said first-mentioned current to a valuedifferent in said one sense than the value of said second current whenthe input voltage impressed on said input electrode is reduced to apredetermined value, whereby the direction of current flow through saidwinding is reversed when said input voltage is decreased from saidsubstantial value to saidpredetermined value and when said input voltageis increased from said predetermined value to said substantial value.

11. Electrical control apparatus comprising, in combination, an electrondischarge device including an input electrode and output electrodes,means for impressing an input voltage on said input electrode, an outputcircuit coupled to said output electrodes, a control'device having awinding connected in said output circuit to be traversed by the currentflowing in said output circuit, a priming circuit including a voltagesource for passing a second current through said Winding, said primingcircuit being so connected and arranged that said second current is inopposi-v tion to said first-mentioned current and is of a magnitudesubstantially different in one sense 6 I I Y 9,181,078

' input electrode, an output circuit coupled to said than the magnitude01' said first-mentioned current when any substantial input voltage isimpressed on said input electrode, the resistance of said primingcircuit being so proportioned relative to the resistance of said windingthat no substantial portion of the direct component of the current insaid output circuit is by-passed around said winding and through saidpriming circuit, and means .for changing the magnitude of one oi saidcurrents so that the magnitude of said iirst-mentione'dcurrent isdiiferent in said one sense 'than the value of said-second current whenthe input voltage impressed on said input electrode is reduced to apredetermined value,

5 whereby the direction of current flow through said winding is reversedwhen said input voltageis decreased from said substantial value' to saidpredetermined value and when said input voltage is increased from saidpredetermined value to said substantial value.

12. Electrical oontrolapparatus comprising, in

combination, an electron discharge device includl output "electrodes, anelectro-magnetic control device including a core, a winding and acontrol element operative between two positions, said winding beingconnected and arranged to be traversed by the current flowing in saidoutput circuit, means for passing a second current through said windingvin opposition to said iirstmentioned current and oi a magnitudesubstantially different in one sense than the magnitude of saidfirst-mentioned current when any substantial input voltage is impressedon said input electrode, and'means for changing the magnitude of saidfirst-mentioned current to a value dlflerent in said one sense than thevalue of said second current when the input voltage impressed on saidinput" electrode is reduced to a predetermined value, whereby thedirection oi current flow through said winding is reversed each timesaid input voltage is varied between said sub-. stantial and saidpredetermined values and said control element is positively operatedbetween its said two positions.

. ROSWELL HARRY

